His background is wrapped in mystery. The Knights of the Cross assume that he's about two thousand years old, but are uncertain, as he takes great pains to destroy all of the church's documentation of him every few centuries or so. Based on the supposed time frame, and a comment he makes about chariots, one can assume that he grew up somewhere in Ancient Rome. He is the oldest of the Denarians, and is a fully cooperative host to the fallen angel Anduriel.
He claims to have known and respected Margaret LeFay.
Harry Dresden nicknames him Nick, as in "Old Nick", another name for Satan.
He is of average height and build, with strong and handsome features, and appears to be middle aged. He has dark eyes and short dark hair with hints of silver. He speaks with a "faintly British" accent, and has a "good voice, mellow, and surprisingly deep." He tends to dress in expensive and elegant clothing, and always wears a noose around his throat. He seems to project a calm and vaguely amused demeanor most of the time. He has a wide, vicious smile that Harry once compares to a crocodile's.
He is intelligent, a meticulous planner, patient, and incredibly careful. He plays a long-game, and even when his plans blow up he has usually not lost much, and has gained at least something. He cares more for ideals than material gain, and is very willing to sacrifice others to achieve his goals. He strives to create chaos in the world, and seems to have a particular predilection for plague curses. He's superficially charming, grandiose, manipulative, and incapable of love, empathy, or remorse; generally the caricature of a typical psychopath.
The noose has power like the Shroud, it was the same rope the Betrayer used in Jerusalem.
Per Harry, Nicodemus plays Armageddon lotto: he makes big plans, but plots to make incremental profits along the way.
He hosts the Fallen Angel Anduriel in his head, which prevents aging and gives him access to extended knowledge. He does not use the Denarian "battle form" nor does he demonstrate any strong magical ability, but he can use his shadow (which Anduriel rides) to incapacitate his victims, and fly. He is stronger and faster than a normal human. Anduriel can listen or observe through any living creature's shadow, and passes the information to Nicodemus if he sees fit. It's limited by Anduriel's attention--it has to focus to get details, otherwise it's background noise. A few places are exempt from Anduriel.(ref?)
According to the Knights He usually has three around him at all times, rarely more than five or six of the Denarian coins at once. In Death Masks, he worked with Ursiel (formerly Rasmussen's), whose coin was retrieved by the Knights upon his defeat, Saluriel (formerly Quintus Cassius'), who gave up his coin to the Knights, and the unknown coin that his daughter and second-in-command, Deirdre, has. He also had the coin of Lasciel, which he gave to Harry and was also in church possession, until it was shown to be in Hannah Ascher's hands. He did not, according to Cassius,, have any others, and if he had amass any coins since, they were undoubtedly also retrieved during the aquarium scene.(ref?)
Around his neck, he carries a noose, allegedly the one that Judas Iscariot used to hang himself. This grants him near invulnerability, except for being strangled by the noose itself, which is, in essence, his only weakness. His sword-fighting experience has been honed over a number of centuries, and he would be equal to the likes of Shiro Yoshimo, but even competent swordsmen like Michael Carpenter wouldn't take him on in a one-on-one sword fight and expect to win.(ref?) Despite his calculating nature, he can occasionally let grudges get in the way. He gave Harry the chance to get the Archive back when offered the chance to defile the blade of Shiro, the one rival he truly despised.(ref?) He and Tessa are considered generally rivals, though they are husband and wife.
A group of tongueless human "squires" and demonic guard-dog-like monsters follow him with absolute loyalty.
In the series Edit
- Main article: Death Masks
In Death Masks, he's in Chicago looking for the Shroud of Turin, which he is planning on using to fuel a large plague curse. He kidnaps Harry, and tries to convince him to take up a coin. When Harry refuses, Nicodemus plans on using him as a sacrifice to fuel the spell, but Harry is saved by Shiro. After being defeated by Sanya, Michael, Harry, and Marcone, and losing the Shroud, Nicodemus tosses a coin in front of Michael's son, Little Harry. Harry Dresden picks it up just in time to prevent the boy to do the same.
- Main article: Small Favor
In Small Favor, Nicodemus captures the Baron Johnny Marcone, violating the Accords, with the intention that Mab will force Harry to get involved in the matter. Harry sets up a meeting at the Shedd Aquarium, with the Archive as an intermediary. It's a trap, so that Nicodemus can kidnap her and force her to take a coin. He is successful. Harry renegotiates with Nicodemus: the Archive, in exchange for the eleven coins they acquired at the aquarium, and Fidelacchius. Nicodemus is enticed by the prospect of coming away with everything, and agrees.
They set up another meeting, which takes place on the island of Demonreach. Nicodemus doesn't follow through on his end of the deal - naturally - and orders the rest of the Denarians to attack. Harry shoots fireball rounds into the air, which has the advantage of signaling Hendricks and Gard's helicopter, and scaring the Denarians so that they'll scatter. They get Marcone and the Archive onto the helicopter, followed by Sanya. By the time Michael's going up, the Denarians have regrouped. The helicopter is forced to leave without Harry on it. Harry eventually finds his way to the boat that they came in on. Nicodemus is already waiting for him. Harry discovers that the bag that held the eleven coins was taken earlier by Thorned Namshiel. Nicodemus claims that Tessa and Rosanna betrayed him, and implies that at least one of them are working for the Black Council. He asks Lasciel's shadow to incapacitate Harry, not knowing that the shadow isn't in Harry's brain anymore, and tries to take Fidelacchius from him. When he gets close enough, Harry grabs Nicodemus's noose and attempts to strangle him with it. Deirdre interrupts him as he's doing this, and he tosses Nicodemus overboard, escaping on the boat.
Nicodemus survived the ordeal in Small Favor, although his voice has been damaged slightly, and is now one of the main characters in Skin Game.
- Main article: Skin Game
Nicodemus could possibly be a reference to Saint Nicodemus from the Bible, who helped wrap Jesus in the Shroud of Turin. It's unknown whether the two are the same person, or if it's just a coincidence.
Archleone means something similar to 'roaring lion'. As in: "the devil, as a roaring lion, walketh about, seeking whom he may devour."